But some say these numbers don't reveal the full picture. It "is made difficult by the fact that there isn't any common language for specific levels of food stress," says Mark Nord, a USDA sociologist and chief tracker of hunger trends. "The best popular description for food insecure households are those having trouble at times putting enough food on the table. Many avoid being hungry ... by cutting down on quality, variety, desirability of diets, and perhaps by getting assistance here and there. It's certainly wrong to characterize all of the people who live in those houses as hungry."
These statistics undercount the number of Americans who have experienced hunger in a given year, says Kathleen Gorman, director of the Center for a Hunger-Free America in Kingston, R.I.
For one, America's 744,000 chronically homeless are not counted in the food security survey, and neither are people living on Indian reservations. Hunger among the elderly may also be underreported, experts say, in part because of how older people experience and explain the physical effects of hunger.
Surveys among school nutritionists in Appalachia show that, in some districts, children come to school in the fall weighing 10 percent less than they did when they left school for the summer. "These aren't small groups of people going hungry. These are big groups of people," says Christine Olson, a human ecology professor at Cornell University in Ithaca, N.Y.
The varied reasons of those who admit to going hungry are difficult to package neatly into a lobbying call.
David Gilman, an out-of-work auto mechanic plucking a half-empty can of cat food out of a garbage can near downtown Atlanta, says he's gone hungry "many times" in the past 15 years. What does hunger feel like? "It's like when you're sent to bed without dinner as a kid if you misbehaved," says Mr. Gilman, who says he struggles with drug addiction.